The primary objective of our work will be to analyze the mechanism by which aberrant proteins are degraded by Escherichia coli. This kind of protein degradation depends in some way on a source of energy; and it is the elucidation of the energy requirement that is of primary interest to us. Detection of the relevant proteases depends on use of the appropriate substrates. We use fragments of the enzyme Beta-galactosidase produced by various mutations in the Z gene or by heat cleavage of the native molecule. The enzymes that degrade these substrates in vitro are being purified, together with other components of the energy-dependent system.